Preparation of purified polyesters



meme 13, 1949 PREPARATION OF PURIFIED POLYESTERS David w. Young, Roselleand William J. Sparks,

Cranford, N..J.,. assig nors to Standard Oil Development Company,acorporation of Delaware No Drawing. Original application January 15,

1944, Serial No. 518,393.

Divided and this application March 3, 1945, SerialNo. 580,918

1 This invention relates to the solvent separation of high molecularweight organic compounds containing carbon and hydrogen and someinorganic element such as oxygen or nitrogen, and having molecularweight above 2,000, and to the use of the resulting separated productfor various purposes. More particularly the invention relates to thesolvent precipitation of high molecular weight polyesters of a dibasicacid and a glycol, in order to recover therefrom a product substantiallycompletely soluble in highly paraffinic oils, especially of thelubricating oil boiling range, even at low temperature, in other words,a'polymer that does not settle out of solution at low temperatures orhigh temperatures in a high viscosity index mineral oil. The originalapplication Serial No. 504,754,

. Claims. (01. 200-428.5)

filed October 2, 1943, now Patent No. 2,424,588, of

which the present application is a' continuationin-part, discloses thepreparation of certain types of polyesters, such as made by condensingdilinoleic acid with ethylene glycol or decamethylene glycol, and theuse of the resulting products in hydrocarbon compositions such aslubricating oils, gas oils, paraffin wax, asphalt, etc.

The polyesters chiefly described in that applicatio and preferred foruse in the present invention, are those made from dimeric fatty acids'or esters thereof, such as made by Bradley and Johnson (Ind. Eng. Chem,33, 86 (1941)),fo'r the preparation of methyl dilinoleate fromdehydrated castor oil. Soy bean oil is also satisfactory,

and is even preferred.

The following is given as a specific example of the preparation of asuitable dimer acid and subsequent condensation with a glycol to producethe preferred type of polyester. Soy bean oil is converted bymethanolysis to methyl esters, as by heating to 70 C. with a'liberalexcess of methanol in the presence of a substantial portion of sodiummethylate for several hours, and then the distilled methyl esters arepolymerized by heating to 300 C. with a suitable catalyst such as 0.3%of anthraquinone, for a'suitable period such as about v-30 hours.Unpolymerized esters are then removed by distillation under reducedpressure of 1-5 mm., and the residual methyl dilinoleate is carefullyfractionated in a short path pot still (a modified-alembic flask) at 2to 50 microns, or in a cyclic molecular still at 2 .to 5 microns. Theseveral distilled dimer methyl esters of soy bean oil, i. e., methyldilinoleate, had

an-index of refraction of ND 1.4766. This dimer acid ester is then usedas raw material in the following experimental work.

. Example 1 A mixture of 3'7 grams of the methyl dilinoleate describedabove and 11.2 grams of decamethylene glycol was heated with about 0.25gram of para-toluene sulfonic acid as catalyst, under nitrogen, forabout 98 hours. A general stream of nitrogen through the reaction massserved to stir the mixture and to facilitate removal of alcohol formedin the reaction; No air or oxygen was present in the reaction at anytime. The resulting polyester had a molecular weight'of about 22,500 byviscosity test; it was soluble in chloroform at room temperature andinsoluble in Barosa 43 mineral oil (a highly parafiinic lubricating oilhaving a viscosity of 43 seconds Saybolt at 210 F. and a viscosity indexof about 110 or 112). However, a 6% solution of such polyester in suchparaflinic oil, which gradually cooled, showed a cloud point of 15 C.

The primary object of the present invention is to subject such apolyester to solvent separation in order to obtain therefrom a fractioncompletely soluble in highly parafflnic oil even at ex-' tremely lowtemperatures,

Thirty grams of the polyester thus obtained was dissolved in 200 gramsof Barosa 43 mineral oil at 140 C. The mineral oil had been saturatedwith nitrogen at room temperature, and nitrogen was added to the oilsolution as the temperature was increased to 140 C. This was for thepurpose of avoiding any possibility of oxidation of the polyestersduring the solvent separation. The polymer-oil mixture was then placedin a 1-liter flask under an atmosphere of nitrogen and then placed in anice-box at about 15-20 F. for 17 hours, during which time some of thepolyesters separated out of solution and settled to the bottom of theflask while other particles of 'precipitated polyesters remainedsuspended in the oil. The cold mixture was filtered through paper and alayer about 10 mm. thick of Hy-Flow, which is a calcined diatomaceousea: th, at about 15-20 C., using vacuum to assist in the filtration. Thefiltrate which was then only slightly turbid was treated with about 15%by volume of dibutoxy ethyl phthalate and about 50% by volume of 99%isopropyl alcohol, in order to precipitate the rest of the polyesterwhich was substantially completely dissolved in the Barosa mineral oil.The dibutoxy ethyl phthalate was merely used to solubilize the alcoholinto the polymer-oil blend. The amount of soluble polyester thusrecovered was about 17 grams and it had an average molecular weight ofabout 9,000.

Ezample 2 The solvent-precipitated soluble polyester made as describedabove in Example 1 was tested in solution in various types of mineraloil. when dissolved in various concentrations ranging from 1 to 5% in aparaiilnic lubricating oil base stock 4 test is known as cm (cooperativefuel research) Fuel #3. v

The soluble polyester of this invention has a number of other valuableproperties, such as good consisting of 90% of a.v Pennsylvania neutralviscosity data was obtained. I

TABLEI Solutions soluble polyester in lubricating oil Saybolt Viscosityl ASTM Sec.

Pou Cloud, at l00 at 2l0 v I 6F 0F 0F. 01;

Test on +30 +34 185.2 46.82. 103 Test og+ -1%a 1 m su;r -20 +32 210.150.47 126.5 Test o osmru ifln i. 15 +32 280.6 68.84 133 Test 0'] 5.0 o

enerjinflffnfljn 0 +32 408.9 78.92 145 I Converted from Kinematic.

The above table shows that this soluble polyester is a potentV. I.improver since it increased the viscosity index from 103 up to 145 in 5%concentration, and also has very substantial pourdepressing properties,obtaining the lowest pour point in a concentration of about 1% (havingreduced the pour point from +30 F'. to 20 F.) and even has a slighteffect in lowering the cloud point of the oil from +34 to +32. Thisslight lowering of the cloud point is not of very substantial magnitude,but is significant because very many lubricating oil additives havequite a reverse effect, namely of increasing the cloud point if theyhave any effect at all thereon.

Example 3 In order to study further the cloud depressing effect, thesoluble polyester was dissolved at various concentrations ranging from0.5% to 6.3%, in a high octane number Diesel fuel base stock (having acetane number of 59.7), which is a highly paraihnic oil. The cloud pointdata obtained were as follows:

TABLE II Diesel fuel 4.2 C. Diesel fuel 0.5% soluble polyester -7.3 C.Diesel fuel 1.4% soluble polyester 5.8 C. Diesel fuel 3.0% solublepo'yester 5.0 C. Diesel fuel 6.3% soluble polyester 4.2 C.

These data indicate that the soluble polyester has a very pronounced andhighly unexpected effect in lowering the cloud point of the parafflm'cDiesel fuel base stock, especially in low concentration up to about 0.5%which lowered the cloud point from 4.2 C. to 7.3 C. Although data onlower concentrations is not available at present, it is believed thateven lower cloud points are obtainable with concentrations compatabilitywith other additives in lubricating oil solutions, such as dyes, andpolymerized silicones 62 0 Cz s Czlli etc., and resistance to mechanicalbreakdown of molecular weight by shearing. It also has some value as adetergent in lubricating oil compositions subjected to unusually severeoperating conditions such as high temperature, as in the case of Dieselengine lubricants; it is also useful as a tackiness additive inlubricating greases, cylinderlubricants, wax compositions, asphalticcompositions, ,etc. It may be used to good advantage as a rubbercompounding agent, and it may also be used for various other purposesfor which the original mixed polyester was described as useful in theoriginal application 504,754. It is also useful in solution in refinedkerosene or gas 011 base stocks as a gun recoil oil.

In carrying out the solvent precipitation of this invention as describedabove, it is possible to vary the process by using other solvents thanthe Barosa 43 paraffinic lubricating oil. For instance other parafiiniclubricating oils having a V. I. of about 100 may be used or lighterparaffinic mineral oil fractions may be used, such as a parafilnic gasoil or a petroleum ether or other types of paraflinic naphtha, or evenliquefied gaseous hydrocarbons such as propane, butane, etc., may beused, in which latter case the technique used may be similar to thatused when the propane precipitation of asphalt from lubricating oilstops, namely by heating the mixture to effect complete solution, andthen cooling and/or reducing the pressure to precipitate out the leastsoluble polyester fractions which normally tend to precipitate out ofthe parafilnic lubricating oil solution at low temperature. If desired,even naphthenic or aromatic oils or halogenated hydrocarbons such aschloroform and the like may be used, or mixtures of various hydrocarbonoils or other solvents may be used. In case a material is used ofsoluble polyesters ranging from about 0.2% to 0.4%. These polyestersalso raise the cetane number of gas oils used as Diesel fuel basestocks. The Diesel fuel base stock used in the above as solvent whichcompletely dissolves the mixed polyesters even at low temperature, thena small amount of non-solvent or anti-solvent is added to the solutionin order to cause precipitation of the least soluble polyester fraction.Suitable non-solvents include the lower alcohols, such as methanol,ethanol, isopropyl alcohol, etc., or lower kctones such as acetone andthe like, or ordinary water, or mixtures.

If desired, the precipitated insoluble polyester fraction may beseparated from the residual solution by settling and decanting,followed, if desired, by washing with a highly paraflinic oil, e. g.,naphtha, petroleum ether, or a lube oil fraction.

Although separation of the polyesters by solvent precipitation as abovedescribed is preferred, solvent extractions may also be used under somecircumstances, such as by contacting the polyester with a highlyparaffinic oil at low temperature, such as 0-15" F. in order to extractthe fractions of polyester which are soluble in the paraflinic oil andto leave undissolved the fractions which are insoluble in such an oil.Solvent extraction I tion of 1.4

' of polyesters zene, alcohol mixtures, etc.

the crude or mixed polyester,

In preparing various alternative raw materials may be used, such as aremore fully described in original application 504,754, mentioned abovewhich lists a number of glycols or dihydroxy organic com- 1. Process ofpreparing purified polyesters of V thelpolycarboxylic acid-glycoltypehaving 800d pounds which may be used ranging fromethylene glycol tohigher aliphatic glycols such as 12- hydroxy stearol or higher, as wellas other compounds containing aromatic or mixed aromatic aliphaticorganic groups between the two hydroxyl Various. saturated as well asunsaturated fatty acids may be used in preparing the dimeric fattycompounds having an organic preferably aliphatic or mixed aliphatic,aromatic hydrocarbon, group between two COO groups representing eithercarboxyl group or lower aliphatic, e. g., methyl, ester group.

Although it is not intended that the invention be'unnecessarily limitedby any theories as to the operation of the invention,'it is believedthat the highly are'partlydue to the removal by solventprecipitation ofpolyesters containing cross-linkages whi h tend .to cause gel formation-or insolubility, and partly due to the removal of polyesters (whenformulated from promote insolubility, such as carboxyl group,'becausethe insoluble polyester thrown down by solvent precipitation gave anacid titration whereas the soluble polyester gave a neutral.

titration. In the experimental work the low toxy ethyl phthalate-alcoholnon-solvent procedure and then titrated at 25 C. with 0.1 N alcoholicpotassium hydroxide using phenolphthalein as indicator. The solvent forthe reaction was dry chloroform. This procedure has been used by Paul J.Flory (see Journal of the American Chemical Society, vol. 62, page 1059,May 1940) to determine the end group present in other polyesters.Results show that grams' of the soluble polymer gave 0.0 ml. titrationto end point with 0.1 N alcoholic potassium hydroxide, while 5 grams ofthe oil-insoluble'polymer gave a titraml. of 0.1 N KOH. Although theinvention is believed particularly applicable to the solvent separationof polyesters made by the condensation of a glycol with a dimeric fattyacid or ester, especially one having more than carbon atoms between thetwo COO groups, the invention is considered broadly applicable to thesolventseparation of other types having a molecular weight, above 2,000,preferably between 6,000 and 30,000, such as polyesters made oils. In aneven broader sense it may be applied to all types of high molecularweight organic compounds of carbon and hydrogen which also by thepolymerization of fatty unexpected advantages of the invention the dimeracid and gly- .001) containing terminal groups which tend to solubilityin parafllnic peratures from acrude polyester mixturecontaining amajorproportion of polyesterhaving a molecular weight above 2,000 andhaving good oil solubility but having admixed therewith a minorproportion of polyester constituents having poor solubility, whichcomprises dissolving said crude mixture in a lightparafllnic'mineral'base lubricating oil fraction, cooling the resultantsolution to a sufliciently low temperature to cause precipitation'ofless soluble polyester-fractions, filtering out and thereafter adding tothe residual solution a lower aliphatic alcohol anti-solvent and asolubilizing agent for said the soluble polyester from the mineral oil.

-2. A process according to claim 1 hich comprises dissolving the entirecrude polyester mixture at an elevated undesired polyester fraction.

having good solubility in an average molecular weight of morecondensation of decamethylene glycol witha: di-

merized unsaturated higher fatty acid, which comprises dissolving saidcrude polyester mixture at elevated temperature in a highly parafllnichydrocarbon base stock having a viscosity index of at least 100, coolingthe resultant solution to a temperature of at least as low as 15 F.thereby causing precipitation of less soluble polyester frac-- tions,separating the precipitated-polyester fraction from the residualsolution by filtration, adding to the residual solution a loweraliphaticalcohol and asolubilizlng agent for said alcohol to renderthe dissolvedpolyester insoluble and thereby precipitating the said dissolvedpolyester from said solution.

4. Process according .toclaim 3 applied to the purification ofpolyesters formed by condensation of methyl dllinoleatewithdecamethylene glycol;

5. The process of preparing purified polyesters having good solubilityin highly parafllnic mineral oil at temperatures as-low as 15 F. from acrude polyester mixture 3,000 and formed by the condensation ofdecamethylene glycol with a dimerized unsaturated higher fatty acidwhich comprises dissolving the said crude polyester mix- I ture at anelevated temperature in a highly parafcontain oxygen and/or nitrogen,including synto the specific examples which have been given merely forthe sake of illustration, but only by the appended claims.

finic hydrocarbon basestock having a viscosity index of at least 100,cooling the resultantv solution to a temperature at least as low as 15F. thereby causing precipitation of less soluble polyester'fractions,separating the precipitated polyester fractions from the residualsolution by filtration, adding to the residual solution about 50% byvolume of isopropyl alcohol and about 15% by volume of dibutoxy-ethylphthalate to render the dissolved polyester insoluble and therebyprecipitating the said dissolved polyester from said solution.

DAVID W. YOUNG. WILLIAM J. SPARKS.

(References on following page) lubricating oils at low tem-,

said precipitated polyester fractions,

anti-solvent to precipitate temperature in a light paraf- *flnic oil"fraction having preferential solubility for a desired polyesterfraction; and cooling the. resultant solution to precipitate the lesssoluble having anaverage molec-' ular weight of more than 7v 8REFERENCES CITED FOREIGN PATENTS The following references are of recordin the Number Country Date file of this patent? 428,864 Great BritainUNITED STATES PATENTS 5 OTHER REFERENCES Number Name Date Bradley etaL;Ind. 81 Eng. Chem January 1941,

2,123,641 Wiezevich July 12,1938 volume 33, No. 1, pages 86-89."2,152,683 Eichwald Apr. 4, 1939 Cowan and Falkenburg: Oil and Soap,August 2,352,883 Bolley July 4, 1944 1943, pages 153-157. 2,384,595Blair Sept. 11.- 1945 2,394,909 Gleason Feb. 12, 1946 2,424,588 Sparkset a] July 29, 1947

